It appears most young foals born on farms with endemic Lawsonia intracellularis could be protected from equine proliferative enteropathy (EPE), a spreading intestinal disease caused by the bacterium, provided they ingest colostrum containing antibodies. Nicola Pusterla, DVM, PhD, Dipl. ACVIM, associate professor in the department of Medicine and Epidemiology at the University of California, Davis, School of Veterinary Medicine, discussed this issue at this year's American College of Veterinary Internal Medicine (ACVIM) Forum, held June 4-7 in San Antonio, Texas.

Equine proliferative enteropathy is an emerging disease in foals and has been the cause of multiple disease outbreaks over the past several years in North America, Europe, Australia, and South Africa. A wide range of clinical signs can be associated with the disease, including diarrhea, dehydration, lethargy, colic, progressive weight loss, rough hair coat, poor body condition, and pendulous abdomen (potbelly appearance). Adult horses can get the disease as well.

In an attempt to document L. intracellularis exposure in foals, Pusterla and colleagues evaluated blood and fecal samples from 68 mare and foal pairs on a farm with endemic EPE.

The researchers obtained blood samples from the mares at the time of foaling and from foals before and after the colostrum consumption. Subsequently, they collected blood samples on a monthly basisfrom all foals for 11 months. Researchers also collected fecal samples from mares at time of foaling, and all foals at birth and once monthly for the duration of the study.

Researchers tested the blood samples for the presence of antibodies against L. intracellularis, and they tested fecal samples for the presence of the bacterium itself.

Of the 68 mares, 54.4% had positive titers against L. intracellularis at the time of foaling, and all foals were negative prior to ingesting colostrum. After colostrum ingestion, 53.7% of foals had colostrum-derived antibodies that persisted transiently for up to three months postpartum.

"During the 11-month study, one-third of foals (22.7%) showed evidence of natural exposure to L. intracellularis, but none of the foals developed clinical signs of EPE, despite the high exposure rate," said Pusterla.

On farms with endemic EPE, the exposure rate of resident broodmares and their foals is high. However, the number of clinically affected animals is generally low.

Pusterla explained, "This study revealed that colostral antibodies specific to L. intracellularis are passively transferred to foals on endemic farms and our evidence suggests that these antibodies may protect against the disease during the pre-weaning period."

Further, Pusterla and colleagues showed that healthy broodmares and foals do not commonly shed L. intracellularis in their feces; therefore, they do not represent a likely source of infection to susceptible animals.

The results of this study were presented in Pusterla's oral presentation titled, "Temporal Detection of Lawsonia intracellularis Using Serology and Real-Time PCR in Thoroughbred Horses Residing on a farm Endemic for Equine Proliferative Enteropathy."

About the Author

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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